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Better getPointResolution default when no transform available #11811

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merged 5 commits into from Dec 13, 2020
Merged

Better getPointResolution default when no transform available #11811

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2bb8aa0
Better default when no transform available
mike-000 Dec 7, 2020
884799d
Add ScaleLine (based on projection units)
mike-000 Dec 8, 2020
519e10b
tidier comments
mike-000 Dec 9, 2020
a9adb18
Test projections without transforms
mike-000 Dec 10, 2020
51db8f9
Test projections without transforms
mike-000 Dec 10, 2020
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7 changes: 7 additions & 0 deletions examples/wms-no-proj.js
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Expand Up @@ -4,6 +4,7 @@ import Projection from '../src/ol/proj/Projection.js';
import TileWMS from '../src/ol/source/TileWMS.js';
import View from '../src/ol/View.js';
import {Image as ImageLayer, Tile as TileLayer} from '../src/ol/layer.js';
import {ScaleLine, defaults as defaultControls} from '../src/ol/control.js';

const layers = [
new TileLayer({
Expand Down Expand Up @@ -37,12 +38,18 @@ const layers = [
// projection object. Requesting tiles only needs the code together with a
// tile grid of Cartesian coordinates; it does not matter how those
// coordinates relate to latitude or longitude.
//
// With no transforms available projection units must be assumed to represent
// true distances. In the case of local projections this may be a sufficiently
// close approximation for a meaningful (if not 100% accurate) ScaleLine control.

const projection = new Projection({
code: 'EPSG:21781',
units: 'm',
});

const map = new Map({
controls: defaultControls().extend([new ScaleLine()]),
layers: layers,
target: 'map',
view: new View({
Expand Down
33 changes: 19 additions & 14 deletions src/ol/proj.js
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Expand Up @@ -212,20 +212,25 @@ export function getPointResolution(projection, resolution, point, opt_units) {
projection,
get('EPSG:4326')
);
let vertices = [
point[0] - resolution / 2,
point[1],
point[0] + resolution / 2,
point[1],
point[0],
point[1] - resolution / 2,
point[0],
point[1] + resolution / 2,
];
vertices = toEPSG4326(vertices, vertices, 2);
const width = getDistance(vertices.slice(0, 2), vertices.slice(2, 4));
const height = getDistance(vertices.slice(4, 6), vertices.slice(6, 8));
pointResolution = (width + height) / 2;
if (toEPSG4326 === identityTransform && units !== Units.DEGREES) {
// no transform is available
pointResolution = resolution * projection.getMetersPerUnit();
} else {
let vertices = [
point[0] - resolution / 2,
point[1],
point[0] + resolution / 2,
point[1],
point[0],
point[1] - resolution / 2,
point[0],
point[1] + resolution / 2,
];
vertices = toEPSG4326(vertices, vertices, 2);
const width = getDistance(vertices.slice(0, 2), vertices.slice(2, 4));
const height = getDistance(vertices.slice(4, 6), vertices.slice(6, 8));
pointResolution = (width + height) / 2;
}
const metersPerUnit = opt_units
? METERS_PER_UNIT[opt_units]
: projection.getMetersPerUnit();
Expand Down